Get the index of a certain value in an array in PHP

Question

I have an array:

$list = array('string1', 'string2', 'string3');

I want to get the index for a given value (i.e. 1 for string2 and 2 for string3)

All I want is the position of the strings in the array

string1 is 0
string2 is 1
string3 is 2

How to achieve this?

this is old .... but I wold like to know why: _"I tried array_search but it was no use"_ — dsdsdsdsd, Feb 13 '14 at 08:22
If you have an associative array, as I did, this answer helps: https://stackoverflow.com/a/3365793/470749 — Ryan, Jan 08 '20 at 15:32

score 217 · Accepted Answer · edited Jan 28 '19 at 11:13

217

array_search is the way to do it.

array_search ( mixed $needle , array $haystack [, bool $strict = FALSE ] ) : mixed

From the docs:

$array = array(0 => 'blue', 1 => 'red', 2 => 'green', 3 => 'red');

$key = array_search('green', $array); // $key = 2;
$key = array_search('red', $array);   // $key = 1;

You could loop over the array manually and find the index but why do it when there's a function for that. This function always returns a key and it will work well with associative and normal arrays.

edited Jan 28 '19 at 11:13

ashleedawg

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answered Jun 02 '10 at 15:43

RaYell

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25

This returns the key, not the index. In your example the key is conveniently the index of the value. – Jorge Ferreira Jun 02 '10 at 15:47
1

@smink, the OP's array is a non-associative array, so it works fine. – Matthew Flaschen Jun 02 '10 at 15:48
1

sorry, i didn't specify the type of array. The array i use is a multi-dimensional array please see my answer for the solution – Aakash Chakravarthy Jun 03 '10 at 04:38
I have this type of array : [ 0 => { id : 1, name : something}, 1 => {.....}, ...]. is this possible to find key/index like array_search("name"=>something,$array) ? – lazzy_ms Jun 14 '18 at 06:18
How about if the array has child ? – questionasker May 08 '20 at 05:35

score 23 · Answer 2 · answered Jun 02 '10 at 15:46

If you're only doing a few of them (and/or the array size is large), then you were on the right track with array_search:

$list = array('string1', 'string2', 'string3');
$k = array_search('string2', $list); //$k = 1;

If you want all (or a lot of them), a loop will prob do you better:

foreach ($list as $key => $value) {
    echo $value . " in " . $key . ", ";
}
// Prints "string1 in 0, string2 in 1, string3 in 2, "

Brian Berneker · Answer 3 · 2021-01-26T20:13:28.723

18

The problem is that you don't have a numerical index on your array.
Using array_values() will create a zero indexed array that you can then search using array_search() bypassing the need to use a for loop.

$list = ['string1', 'string2', 'string3'];
$index = array_search('string2',array_values($list));

edited Jan 26 '21 at 20:13

answered Mar 20 '15 at 15:08

Brian Berneker

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Bill Karwin · Answer 4 · 2010-06-02T16:20:42.087

Other folks have suggested array_search() which gives the key of the array element where the value is found. You can ensure that the array keys are contiguous integers by using array_values():

$list = array(0=>'string1', 'foo'=>'string2', 42=>'string3');
$index = array_search('string2', array_values($list));
print "$index\n";

// result: 1

You said in your question that array_search() was no use. Can you explain why? What did you try and how did it not meet your needs?

score 10 · Answer 5 · answered Jan 17 '14 at 22:37

// or considering your array structure:

$array = array(
  'string1' => array('a' => '', 'b' => '', 'c' => ''),
  'string2' => array('a' => '', 'b' => '', 'c' => ''),
  'string3' => array('a' => '', 'b' => '', 'c' => ''),
);

// you could just

function findIndexOfKey($key_to_index,$array){
  return array_search($key_to_index,array_keys($array));
}

// executed

print "\r\n//-- Method 1 --//\r\n";
print '#index of: string1 = '.findIndexofKey('string1',$array)."\r\n";
print '#index of: string2 = '.findIndexofKey('string2',$array)."\r\n";
print '#index of: string3 = '.findIndexofKey('string3',$array)."\r\n";

// alternatively

print "\r\n//-- Method 2 --//\r\n";
print '#index of: string1 = '.array_search('string1',array_keys($array))."\r\n";
print '#index of: string2 = '.array_search('string2',array_keys($array))."\r\n";
print '#index of: string3 = '.array_search('string3',array_keys($array))."\r\n";

// recursersively

print "\r\n//-- Method 3 --//\r\n";
foreach(array_keys($array) as $key => $value){
  print '#index of: '.$value.' = '.$key."\r\n";
}

// outputs

//-- Method 1 --//
#index of: string1 = 0
#index of: string2 = 1
#index of: string3 = 2

//-- Method 2 --//
#index of: string1 = 0
#index of: string2 = 1
#index of: string3 = 2

//-- Method 3 --//
#index of: string1 = 0
#index of: string2 = 1
#index of: string3 = 2

This answer has deviated too far from the asked question. The question is not talking about associative arrays. — mickmackusa, Jan 17 '23 at 22:16

score 1 · Answer 6 · answered Jun 02 '10 at 15:42

1

Try the array_keys PHP function.

$key_string1 = array_keys($list, 'string1');

answered Jun 02 '10 at 15:42

Evernoob

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aren't those parameters [reversed](http://www.php.net/manual/en/function.array-search.php)? – ashleedawg Jan 28 '19 at 10:28
@ashleedawg No you have misread, `array_keys` is different to `array_search` – A Friend Nov 20 '19 at 19:43

score 1 · Answer 7 · answered Jun 02 '10 at 15:49

1

Could you be a little more specific?

$key = array_search('string2',$list)

works fine for me. Are you trying to accomplish something more complex?

answered Jun 02 '10 at 15:49

Jeff

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Get the index of a certain value in an array in PHP

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